Hard as it is to believe, Windows XP (not sure about Vista) is configured by default so that 20% of the bandwidth is "reserved" exclusively for use by Windows. This is absolutely ridiculous. Luckily, if you are using Windows XP Pro, you can get this bandwidth back and see a noticeable increase in connection speed. If you are not on the Pro edition, you are stuck, you can thank Bill Gates for taking 20% of your bandwidth for no reason. For the rest of you, here's how to get that 20% bandwidth back.

1 - Log in as an administrator, not as a user with administrative permissions, but an actual admin.

2 - Go to Start -> Run (or hit Windows + R) and type in gpedit.msc to run the Group Policy program.

3 - In the left panel, expand the windows like so: (+) Administrative Templates, (+) Network and then single click (just highlight) the entry called QoS Packet Scheduler.

4 - In the right panel, you will see an entry called Limit reservable bandwidth. If you single click on this, it will describe to you how it is reserving 20% of your bandwidth for the system. Double click on this row and you can adjust the settings. You want to select the radio button labeled Enabled (when this feature is not enabled, it automatically reserves 20% of the bandwidth) and then adjust the Bandwidth limit (%) down to 0.

5 - When you are done, click the Apply button, then OK.

You have not gotten back that 20% of your bandwidth. If you go to a bandwidth speed test site before and after doing this, you should see a nice improvement in the speed of your connection.